U.S. patent number 7,443,819 [Application Number 11/087,151] was granted by the patent office on 2008-10-28 for managing scrambling codes during serving radio network subsystem relocation.
This patent grant is currently assigned to Lucent Technologies Inc.. Invention is credited to Thomas Hempel, Sudeep Palat, Mirko Schacht.
United States Patent |
7,443,819 |
Hempel , et al. |
October 28, 2008 |
Managing scrambling codes during serving radio network subsystem
relocation
Abstract
The present invention provides a method and an apparatus for
managing relocation of one or more scrambling codes in a spread
spectrum wireless communications system. The method comprises
detecting an indication for a serving radio network subsystem
relocation that causes a user equipment to leave a first radio
network controller and selectively transiting, through an
intermediate transition, at least one scrambling code of the one or
more scrambling codes associated with an uplink from the first
radio network controller to a second radio network controller for
the user equipment in response to the indication. The first radio
network controller may maintain three pools of scrambling codes,
namely, a first pool of one or more relocated scrambling codes
(SCs), a second pool of one or more free scrambling codes and a
third pool for each of one or more used scrambling codes. By
avoiding an early reuse, an uplink scrambling code may be assigned
to a particular UE because a target radio network controller, i.e.,
a new serving radio network controller may use the same scrambling
code as long relocated user equipment maintains a current call. In
this way, an uplink scrambling code defined for a serving radio
network subsystem relocation procedure based on 3GPP standards may
be consistent across disparate vendor solutions.
Inventors: |
Hempel; Thomas (Neumarkt,
DE), Schacht; Mirko (Allersberg, DE),
Palat; Sudeep (Swindon, GB) |
Assignee: |
Lucent Technologies Inc.
(Murray Hill, NJ)
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Family
ID: |
36571732 |
Appl.
No.: |
11/087,151 |
Filed: |
March 23, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060215625 A1 |
Sep 28, 2006 |
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Current U.S.
Class: |
370/331; 370/342;
455/436 |
Current CPC
Class: |
H04B
7/2628 (20130101); H04W 36/10 (20130101) |
Current International
Class: |
H04Q
7/00 (20060101) |
Field of
Search: |
;370/328,329,331
;455/436-439,442-443 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1626514 |
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Feb 2006 |
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EP |
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WO 2004/105280 |
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Dec 2004 |
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WO |
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Other References
European Search Report Dated Jun. 16, 2006 (Serial No. 06241053.2).
cited by other .
"Cold Code Generator Reference Design", Mar. 2003, Version 1.0,
Altera Corporation. cited by other.
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Primary Examiner: Nguyen; Duc
Assistant Examiner: Wang; David
Claims
We claim:
1. A method of managing relocation of one or more scrambling codes
in a spread spectrum wireless communications system, the method
comprising: detecting an indication for a serving radio network
subsystem relocation that causes a user equipment to leave a first
radio network controller; in response to said indication,
selectively transiting, through an intermediate transition, said at
least one scrambling code of said one or more scrambling codes
associated with an uplink from said first radio network controller
to a second radio network controller for said user equipment;
transitioning said at least one scrambling code from a first pool
of one or more relocated scrambling codes to a second pool of one
or more free scrambling codes through a third pool of one or more
used scrambling codes at said first radio network controller;
moving a first scrambling code associated with said user equipment
into said first pool of one or more relocated scrambling codes; and
in response to moving said first scrambling code, moving out a
respective oldest scrambling code from said first-in-first-out
shift register; determining whether said second pool of one or more
free scrambling codes is empty; and if empty, removing a second
scrambling code from said first pool of one or more relocated
scrambling codes.
2. A method, as set forth in claim 1, wherein selectively
transiting, through an intermediate transition, at least one
scrambling code further comprises: reassigning said at least one
scrambling code on said second radio network controller from said
one or more scrambling codes at said first radio network controller
based on a desired handling of said at least one scrambling code by
said first radio network controller.
3. A method, as set forth in claim 1, wherein selectively
transiting, through an intermediate transition, at least one
scrambling code further comprises using the first-in-first-out
shift register.
4. A method, as set forth in claim 1, further comprising: assigning
said second scrambling code to said user equipment from said first
pool of one or more relocated scrambling codes.
5. A method, as set forth in claim 4, wherein assigning said second
scrambling code further comprising: in response to a user starting
a call at said user equipment, transiting said second scrambling
code to said third pool of one or more used scrambling codes.
6. A method, as set forth in claim 4, further comprising: obtaining
a desired assignment of said first and second scrambling codes
within each of said first and second radio network controllers
among said one or more scrambling codes.
7. A method, as set forth in claim 1, further comprising:
performing scrambling code administration during said serving radio
network subsystem relocation without using additional signaling
between said first and second radio network controllers.
8. A radio network controller associated with a wireless network in
a spread spectrum wireless communications system, said radio
network controller comprising: a controller; and a storage coupled
to said controller, said storage instructions to detect an
indication for a serving radio network subsystem relocation that
causes a user equipment to leave a first radio network controller;
in response to said indication, selectively transit, through an
intermediate transition, said at least one scrambling code of said
one or more scrambling codes associated with an uplink to a second
radio network controller for said user equipment; transition said
at least one scrambling code from a first pool of one or more
relocated scrambling codes to a second pool of one or more free
scrambling codes through a third pool of one or more used
scrambling codes; move a first scrambling code associated with said
user equipment into said first pool of one or more relocated
scrambling codes; in response to moving said first scrambling code,
move out a respective oldest scrambling code from a
first-in-first-out shift register; determine whether said second
pool of one or more free scrambling codes is empty; and if empty,
remove a second scrambling code from said first pool of one or more
relocated scrambling codes.
9. A radio network controller, as set forth in claim 8, wherein
said radio network controller further comprises a buffer to manage
a first pool of one or more relocated scrambling codes, a second
pool of one or more free scrambling codes, and a third pool of one
or more used scrambling codes at said radio network controller.
10. A radio network controller, as set forth in claim 8, wherein
said radio network controller is coupled to a base station that
communicates with said user equipment.
11. A radio network controller, as set forth in claim 8, wherein
said radio network controller further comprises: a manager; and a
first-in-first-out shift register that said manager uses to manage
a first pool of one or more relocated scrambling codes, a second
pool of one or more free scrambling codes, and a third pool of one
or more used scrambling codes at said radio network controller.
12. A radio network controller, as set forth in claim 8, wherein
said wireless network is being defined at least in part by a code
division multiple access protocol.
13. A spread spectrum wireless communications system comprising: a
radio network controller associated with a wireless network, said
radio network controller including; a controller, and a storage
coupled to said controller, said storage storing instructions to
detect an indication for a serving radio network subsystem
relocation that causes a user equipment to leave said radio network
controller and to use a buffer to selectively transit, through an
intermediate transition, at least one scrambling code of said one
or more scrambling codes associated with an uplink from said radio
network controller to a second radio network controller for said
user equipment in response to said indication; transition said at
least one scrambling code from a first pool of one or more
relocated scrambling codes to a second pool of one or more free
scrambling codes through a third pool of one or more used
scrambling codes; move a first scrambling code associated with said
user equipment into said first pool of one or more relocated
scrambling codes; in response to moving said first scrambling code,
move out a respective oldest scrambling code from a
first-in-first-out shift register; determine whether said second
pool of one or more free scrambling codes is empty; and if empty
remove a second scrambling code from said first pool of one or more
relocated scrambling codes.
14. A spread spectrum wireless communications system, as set forth
in claim 13, wherein said wireless network comprises an access
network and a core network, said wireless network is being defined
at least in part by a code division multiple access protocol.
15. A spread spectrum wireless communications system, as set forth
in claim 13, wherein said radio network controller further
comprises: a manager that uses said first-in-first-out shift
register to manage a first pool of one or more relocated scrambling
codes, a second pool of one or more free scrambling codes, and a
third pool of one or more used scrambling codes at said radio
network controller.
16. An article comprising a computer readable storage medium
storing instructions that, when executed cause a spread spectrum
wireless communications system to; detect an indication for a
serving radio network subsystem relocation that causes a user
equipment to leave a first radio network controller; and
selectively transit, through an intermediate transition, at least
one scrambling code of said one or more scrambling codes associated
with an uplink from said first radio network controller to a second
radio network controller for said user equipment in response to
said indication; transition said at least one scrambling code from
a first pool of one or more relocated scrambling codes to a second
pool of one or more free scrambling codes through a third pool of
one or more used scrambling codes; move a first scrambling code
associated with said user equipment into said first pool of one or
more relocated scrambling codes; in response to moving said first
scrambling code, move out a respective oldest scrambling code from
a first-in-first-out shift register; determine whether said second
pool of one or more free scrambling codes is empty; and if empty.
remove a second scrambling code from said first pool of one or more
relocated scrambling codes.
17. An apparatus for managing relocation of one or more scrambling
codes in a spread spectrum wireless communications system, the
apparatus comprising: means for detecting an indication for a
serving radio network subsystem relocation that causes a user
equipment to leave a first radio network controller; means for
selectively transiting, in response to said indication, through an
intermediate transition, said at least one scrambling code of said
one or more scrambling codes associated with an uplink from said
first radio network controller to a second radio network controller
for said user equipment; means for transitioning said at least one
scrambling code from a first pool of one or more relocated
scrambling codes to a second pool of one or more free scrambling
codes through a third pool of one or more used scrambling codes;
means for moving a first scrambling code associated with said user
equipment into said first pool of one or more relocated scrambling
codes; means for moving out a respective oldest scrambling code
from a first-in-first-out shift register, in response to moving
said first scrambling code; means for determining whether said
second pool of one or more free scrambling codes is empty; and if
empty. means for removing a second scrambling code from said first
pool of one or more relocated scrambling codes.
Description
FIELD OF THE INVENTION
This invention relates generally to telecommunications, and more
particularly, to wireless communications.
DESCRIPTION OF THE RELATED ART
Typical wireless communications systems or mobile telecommunication
systems provide different types of services to users or subscribers
of a number of user equipment (UE), such as wireless communication
devices. The wireless communication devices may be mobile or fixed
units and situated within a geographic region across one or more
wireless networks. The users or subscribers of mobile units or user
equipment may constantly move within (and outside) particular
wireless networks. To this end, a wireless communications system,
for instance, a spread spectrum wireless communications system,
such as code division multiple access (CDMA) system may allow
multiple users to transmit simultaneously within the same wideband
radio channel, enabling a frequency re-use based on a spread
spectrum technique.
In a spread spectrum wireless communications system, an information
signal between a base station and a UE is multiplied by a spread
spectrum signal. Often spread spectrum systems, such as code
division multiple access (CDMA) systems, spread and/or scramble
data in the information signal by multiplying the information
signal with a spreading and/or scrambling code sequence (scrambling
code sequence), such as a pseudo noise (PN) code which is a binary
sequence that appears random but can be reproduced by the intended
receiving station. When the scrambling code sequence has the same
pulse rate as the information signal, the product of the scrambling
code sequence and the information signal is scrambled, and the
spectrum is unchanged.
When moving within a particular wireless networks, such as a
digital cellular CDMA network, a handover of mobile communications
occurs for a user equipment (UE) upon a user leaving an area of
responsibility of a first cell, namely, into a new cell. At this
point, a serving radio network controller (RNC) of a serving radio
network subsystem (RNS) gets replaced by a target RNC, as a new
access radio network controller for the UE. A serving radio network
subsystem (SRNS) relocation procedure may replace an existing SRNS
by a target RNS. Using radio network subsystems (RNSs), a radio
network controller communicates with a core network (CN). The SRNS
relocation is generally used if a serving RNC and a target RNC are
connected by an interface referred to as Iur for interconnecting
two RNCs within a UTRAN network (UMTS Radio Access Network) and the
target RNC acts as a drift RNC (DRNC). After a new connection to
the target RNC is established, e.g., using an interface called Iub
that interconnects the RNC to a Node B, the Iur connection between
the two radio network controllers is released and the drift RNC
becomes the new serving RNC.
The 3rd Generation Partnership Project (3GPP) standard defines a
serving radio network subsystem relocation procedure, which does
not involve a change of any radio resources assigned for a
corresponding UE procedure that uses signalling protocols based on
3GPP specifications including 3GPP TR 25.931, 3GPP TS 25.331, 3GPP
TS 23.009, 3GPP TS 23.060, 3GPP TS 25.413, and 3GPP TS 25.423. That
is, in this serving radio network subsystem relocation procedure
the user equipment is not involved at all. Therefore, an uplink
scrambling code defined for the serving radio network subsystem
relocation procedure based on these 3GPP standards may not be
consistent with disparate vendor solutions. Because an uplink
scrambling code has to be unique for a particular UE and should be
same for all of the radio links within an active set of the user
equipment, the serving RNC becomes a responsible network entity for
assigning the uplink scrambling code. After a serving radio network
subsystem relocation, a former drift RNC which subsequently becomes
the serving RNC takes over this responsibility.
However, the responsibility of assigning a new uplink scrambling
code throughout the serving radio network subsystem relocation is
not adequately defined in the 3GPP standards. That is, it is not
clear, whether or not a new serving RNC is to assign a new uplink
scrambling code throughout the serving radio network subsystem
relocation and if the old serving RNC is to be made aware that the
uplink scrambling code is not in use any more. Moreover, a possible
loss of signaling messages from a specific user equipment to a
radio network controller or vice versa may occur during serving
radio network subsystem relocation.
One solution to scrambling code administration during the serving
radio network subsystem relocation suggests use of a timer-based
trigger for transiting scrambling codes from the relocated buffer.
Such a solution runs a significant risk of causing a collision
between UEs that may end up using the same scrambling code,
especially in an inter-vendor scenario where the two involved radio
network controllers concerned may follow different policies for
treating the scrambling codes. With such a timer-based solution, a
risk of causing a collision is relatively high, as the particular
scrambling code may become available upon a timer expiry regardless
of the availability of other scrambling codes.
The present invention is directed to overcoming, or at least
reducing, the effects of, one or more of the problems set forth
above.
SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in
order to provide a basic understanding of some aspects of the
invention. This summary is not an exhaustive overview of the
invention. It is not intended to identify key or critical elements
of the invention or to delineate the scope of the invention. Its
sole purpose is to present some concepts in a simplified form as a
prelude to the more detailed description that is discussed
later.
In one embodiment of the present invention, a method is provided
for managing relocation of one or more scrambling codes in a spread
spectrum wireless communications system. The method comprises
detecting an indication for a serving radio network subsystem
relocation that causes a user equipment to leave a first radio
network controller and selectively transiting, through an
intermediate transition, at least one scrambling code of the one or
more scrambling codes associated with an uplink from the first
radio network controller to a second radio network controller for
the user equipment in response to the indication.
In another embodiment, a radio network controller is associated
with a wireless network in a spread spectrum wireless
communications system. The radio network controller comprises a
controller and a storage coupled thereto. The storage may store
instructions to detect an indication for a serving radio network
subsystem relocation that causes a user equipment to leave the
radio network controller and to selectively transit, through an
intermediate transition, at least one scrambling code of the one or
more scrambling codes associated with an uplink from the radio
network controller to a second radio network controller for the
user equipment in response to the indication.
In yet another embodiment, a spread spectrum wireless
communications system comprises a radio network controller
associated with a wireless network. The radio network controller is
similar to one described in an embodiment set forth above.
In still another embodiment, an article comprising a computer
readable storage medium storing instructions that, when executed
cause a spread spectrum wireless communications system to detect an
indication for a serving radio network subsystem relocation that
causes a user equipment to leave a first radio network controller
and to selectively transit, through an intermediate transition, at
least one scrambling code of the one or more scrambling codes
associated with an uplink from the first radio network controller
to a second radio network controller for the user equipment in
response to the indication.
In one exemplary embodiment, an apparatus for managing relocation
of one or more scrambling codes in a spread spectrum wireless
communications system comprises means for detecting an indication
for a serving radio network subsystem relocation that causes a user
equipment to leave a first radio network controller and means for
selectively transiting, through an intermediate transition, at
least one scrambling code of the one or more scrambling codes
associated with an uplink from the first radio network controller
to a second radio network controller for the user equipment in
response to the indication.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be understood by reference to the following
description taken in conjunction with the accompanying drawings, in
which like reference numerals identify like elements, and in
which:
FIG. 1 illustrates a spread spectrum wireless communications system
including a first and a second radio network controllers each
associated with at least one base station within a wireless network
to manage relocation of one or more scrambling codes for
communicating with a user equipment according to one illustrative
embodiment of the present invention;
FIG. 2 schematically depicts a radio frequency transmitter and
receiver based on a code division multiple access protocol for the
base station and the user equipment illustrated in FIG. 1 in
accordance with an exemplary embodiment of the instant
invention;
FIG. 3 schematically depicts a first-in-first-out shift register as
the buffer shown in FIG. 1 consistent with one embodiment of the
present invention;
FIG. 4 schematically depicts one embodiment of the manager shown in
FIG. 1 to manage a first pool of one or more relocated scrambling
codes, a second pool of one or more free scrambling codes, and a
third pool of one or more used scrambling codes at the first and
second radio network controllers; and
FIG. 5 shows a stylized representation of a method for managing
relocation of one or more scrambling codes in the spread spectrum
wireless communications system shown in FIG. 1 at each of the first
and second radio network controllers according to one illustrative
embodiment of the present invention.
While the invention is susceptible to various modifications and
alternative forms, specific embodiments thereof have been shown by
way of example in the drawings and are herein described in detail.
It should be understood, however, that the description herein of
specific embodiments is not intended to limit the invention to the
particular forms disclosed, but on the contrary, the intention is
to cover all modifications, equivalents, and alternatives falling
within the spirit and scope of the invention as defined by the
appended claims.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
Illustrative embodiments of the invention are described below. In
the interest of clarity, not all features of an actual
implementation are described in this specification. It will of
course be appreciated that in the development of any such actual
embodiment, numerous implementation-specific decisions may be made
to achieve the developers' specific goals, such as compliance with
system-related and business-related constraints, which will vary
from one implementation to another. Moreover, it should be
appreciated that such a development effort might be complex and
time-consuming, but may nevertheless be a routine undertaking for
those of ordinary skill in the art having the benefit of this
disclosure.
Generally, a method and apparatus is described for managing one or
more uplink scrambling codes during SRNS relocation. Such a method
and apparatus may be 3GPP standard compliant and consistent with
various vendor solutions. By detecting an indication for a serving
radio network subsystem (SRNS) relocation that causes a user
equipment to leave a first radio network controller, scrambling
code pool manager may enable selective transiting, through an
intermediate transition, of a particular scrambling code for the UE
associated with an uplink from the first radio network controller
to the second radio network controller in response o the indication
for the SRNS relocation. In this way, an uplink (UL) scrambling
code may be assigned to a particular UE. A first RNC may maintain
three pools of scrambling codes, namely a first pool of one or more
relocated scrambling codes (SCs), a second pool of one or more free
scrambling codes and a third pool for each of one or more used
scrambling codes. The scrambling code may be taken from a third
pool of free scrambling codes if this pool is not empty. If the
third pool of free scrambling codes is empty, an UL SC from a FIFO
queue of the relocated UL SC pool may be taken. In both cases,
however, a particular SC may be moved to a third pool of the used
scrambling codes. In some embodiments, a network vendor may deploy
a first manager to implement an assignment scheme of scrambling
codes, which have been relocated to from one RNC to other RNCs,
where early reuse may cause collisions. The first manager may
account for a case where the UE takes a scrambling code to another
RNC by the SRNS relocation.
Referring to FIG. 1, a spread spectrum wireless communications
system 100 is illustrated to include a first and a second radio
network controller 105(1), 105(N) that manage relocation of one or
more scrambling codes for communicating with a user equipment (UE)
110 according to one illustrative embodiment of the present
invention. Each of the first and second radio network controllers
105(1), 105(N) may be associated with one or more base stations,
e.g., Node-Bs within a wireless network 112. Specifically, the
first radio network controller 105(1) may be coupled to a first
plurality of base stations, i.e., Node-Bs 115a (1-m) and the second
radio network controller 105(M) may be coupled to a second
plurality of base stations, i.e., Node-Bs 115b (1-k).
One example of the wireless network 112 includes a digital cellular
network. More specifically, the 3rd Generation Partnership Project
(3GPP) specifications for a wideband code division multiple access
(WCDMA) Universal Mobile Telecommunications Systems (UMTS) defines
a uplink channel that uses a set of specific sequences in spread
spectrum systems, such as a based on a CDMA technique. The user
equipment (UE) 110 may refer to a host of wireless communication
devices including, but not limited to, cellular telephones,
personal digital assistants (PDAs), and global positioning systems
(GPS) that employ the spread spectrum communications system 100 to
operate in the wireless network 112, such as a digital cellular
CDMA network.
Each of the first and the second radio network controller 105(1-N)
may comprise a controller and a storage coupled to that controller.
In particular, the first radio network controller 105(1) may
include a first controller 117(1) and a first storage 119(1).
Likewise, the second radio network controller 105(N) may include a
second controller 117(N) and a second storage 119(N). Furthermore,
the first radio network controller 105(1) may include a first
buffer 122(1) e.g., a first-in-first-out (FIFO) shift register to
selectively transit, through an intermediate transition, at least
one scrambling code (SC) of the one or more scrambling codes and a
first manager 124(1), e.g., a SC pool manager to manage relocation
of the one or more scrambling codes. Likewise, the second radio
network controller 105(N) may include a second buffer 122(N) and a
second manager 124(N).
For example, the first storage 119(1) may store instructions to
detect an indication for a serving radio network subsystem (SRNS)
relocation that causes the user equipment 110 to leave the first
radio network controller 105(1). The instructions may enable the
first manager 124(1) to use the first buffer 122(1) for selectively
transiting, through an intermediate transition, a particular
scrambling code for the UE 110 associated with an uplink from the
first radio network controller 105(1) to the second radio network
controller 105(N) in response to the indication for the SRNS
relocation.
An uplink or a reverse communication link refers to a means for
transmitting information from the UE 110 to a base station, i.e.,
the Node-B 115a(1), for example, over a radio frequency (RF) link
that transports data from the UE 110 to the base station in an
uplink as a portion of a communications link. That is, a RF uplink
or a RF reverse link may indicate the transmission of RF signals.
Example of a RF uplink or a RF reverse link includes a base station
controller (BSC) to a mobile services switching center (MSC) or
from a base transceiver station (BTS) to a BSC.
In one embodiment, the SRNS relocation may be performed for a given
wireless communication device, e.g., the UE 110 in the wireless
network 112, such as a Universal Mobile Telecommunications System
(UMTS) network. The wireless network 112 may comprise a radio
access network 125, e.g., a Universal Terrestrial Radio Access
Network (UTRAN) and a core network (CN) 130, in which the radio
access network and the core network 130 may be logically
separated.
The core network 130 may process voice calls using UMTS mobile
services switching centers (UMTS-MSCs) or may use a data network
such as a General Packet Radio Service (GPRS) network including
serving GPRS support nodes (SGSNs) 140(1) and 140(2). The UE 110
may couple to the core network 130 via the radio access network 125
referred to as a UTRAN. More particularly, the UMTS-MSCs/SGSNs
140(1) and 140(2) may connect to the first and second radio network
controllers 105(1-N) over a conventional interface generally
referred to as Iu interfaces 145(1-2).
However, the SRNS relocation may be responsible for a transfer of
radio resources between a serving RNC, i.e., the first RNC 105(1)
and a target RNC, i.e., the second RNC 105(N) in the wireless
network 112, such as a UMTS network. More specifically, the SRNS
relocation will move the control of a UE wireless connection over
an air interface from a source, for example, the old serving RNC
105(1) to a target or new serving RNC 105(N). Accordingly, both a
control and a user plane may be moved to the target or new serving
RNC 105(N). In this way, the SRNS relocation may handle and
relocate the UE 110 and RNC serving role.
A user plane connection may be established between the target RNC
105(N) and the CN 130. In some embodiments, the user plane
connection may extend between the target RNC 105(N), referred to as
a drift RNC and the core network 130 via the serving RNC 105(1). An
interface, i.e., an Iur interface 150 may be established between
the drift RNC 105(N) and the serving RNC 105(1). The wireless
network 112 may subsequently convert the drift RNC into a new
serving RNC, establishing a direct user plane connection to the CN
130.
The CN 130 may comprise an automatic request (ARQ) unit for
retransmission to handle a potential data loss. Essentially, the
ARQ unit enables a link for communications in which a receiver
requests a transmitter to resend a block of data when errors may be
detected in transmission. During the SRNS relocation, for the
control plane, i.e., involving signaling between the UE 110 and the
serving RNC 105(1), the target RNC 105(N) may become a serving RNC,
providing a signaling link between the UE 110 and the serving RNC
105(1).
In operation, the serving RNC 105(1) may wirelessly communicate
with the UE 110 to provide service data units (SDUs) from the CN
130 to the UE 110. The serving RNC 105(1) may associate a sequence
number (SN) with each of the service data units, and the UE 110 may
be capable of confirming to the serving RNC service data units
received from the serving RNC 105(1). Forwarding information may be
provided by the serving RNC 105(1) to the target RNC 105(N). The
forwarding information may include service data units unconfirmed
as received by the UE 110. In this manner, the target RNC 105(N)
may be designated as the new serving RNC for the UE 110.
A bearer structure may be used by the radio access network 125,
e.g., the UTRAN to carry user data between the UE 110 and the core
network 130. To establish a user plane connection, the
UMTS-MSC/SGSN 140(1) may communicate with the radio access network
125 to form a conventional logical connection, such as a Radio
Access Bearer (RAB), between the UMTS-MSC/SGSN 140(1) and the UE
110. Using the RAB, the first RNC 105(1) may establish a user plane
connection, e.g., an Iu bearer connection, with the core network
130 and a Radio Bearer (RB) Uu connection for the UE 110 based on
logical channels.
Turning now to FIG. 2, a radio frequency (RF) transmitter 200 and a
RF receiver 205 are schematically depicted based on a CDMA protocol
for a base station, e.g., the Node-B 115a(1) and the user equipment
110 illustrated in FIG. 1 in accordance with an exemplary
embodiment of the instant invention. While the transmitter 200
spreads and/or scrambles the information or data signal to produce
a spread spectrum signal for transmission, and the receiver 205
descrambles and/or despreads the spread spectrum signal to retrieve
original information or data.
To this end, in one embodiment, the transmitter 200 incorporates a
coder 210 for processing original data being input, using channel
coding, a bit-level interleaving, a digital modulation functions,
or the alike to produce a RF communication signal 215. The
transmitter 200 further comprises a scrambling code generator 220
that generates one or more scrambling codes, and a multiplier 225
for multiplying the scrambling codes with the output of the coder
210 to produce a wideband or a spread spectrum communication
signal. The transmitter 200 may include a modulator 230 to modulate
the spread spectrum communication signal onto a carrier signal and
an antenna 235 to transmit the spread spectrum signal to the
receiver 205.
The receiver 205 may comprise an antenna 237 to receive the spread
spectrum signal from the transmitter 200 and a demodulator 240 to
demodulate the received spread spectrum signal and generate a
demodulated spread spectrum signal. The receiver 205 may further
comprise a multiplier 245 that multiples the demodulated spread
spectrum signal with the scrambling codes furnished by a scrambling
code generator 250. This multiplication may despread and/or
descramble the demodulated spread spectrum signal, restoring the RF
communication signal 215. The receiver 205 may comprise a decoder
255 that extracts the original data from the receiver 205.
Consistent with one embodiment of the present invention, a
first-in-first-out (FIFO) shift register 300 is schematically
depicted in FIG. 3 as the first buffer 122(1) shown in FIG. 1. As
illustrated in FIG. 3, the FIFO shift register 300 may comprise a
multiplicity of registers 305 to receive re-located scrambling
codes in an indication arrow 310, when the UE 110 relocates from
the first RNC 105(1) to the second RNC 105(N). When the UE 110
initiates a call, and if a pool of free or available scrambling
codes is empty, the removed scrambling code may be sent to a pool
of used scrambling codes, as illustrated by an indication arrow
315. The role of different pools of the scrambling codes, as
controlled by the first manager 124(1) is described below.
As depicted, FIG. 4 schematically illustrates one embodiment of the
first manager 124(1) shown in FIG. 1 to manage a first pool 405 of
one or more relocated scrambling codes, a second pool 410 of one or
more free scrambling codes, and a third pool 415 of one or more
used scrambling codes at the first radio network controller 105(1).
The first manager 124(1) transitions at least one scrambling code
from the first pool 405 of the relocated scrambling codes to the
second pool 410 of the free scrambling codes through the third pool
415 of the used scrambling codes. Based on a desired handling of a
particular scrambling code by the first radio network controller
105(1), in one embodiment, the first manager 124(1) reassigns that
scrambling code on the second radio network controller 105(N) from
the one or more scrambling codes available at the first radio
network controller 105(1).
The first manager 124(1) may move a first scrambling code
associated with the user equipment 110 into the first pool 405 of
the relocated scrambling codes, and in response to moving of the
first scrambling code, a respective oldest scrambling code may be
moved out from the FIFO shift register 300. A determination may be
made as to whether or not the second pool 410 of the free
scrambling codes is empty. If determined to be empty, a second
scrambling code may be removed from the first pool 405 of the
relocated scrambling codes. The second scrambling code may be
assigned to the user equipment 110 from the first pool 405 of the
relocated scrambling codes. In response to a user starting a call
at the user equipment 110, the first manager 124(1) may transit the
second scrambling code to the third pool 415 of the used scrambling
codes. A desired assignment of the first and second scrambling
codes may be obtained within each of the first and second radio
network controllers 105(1-N) among the one or more scrambling
codes, i.e., the total set of scrambling codes. In this manner,
scrambling code administration may be performed during the serving
radio network subsystem relocation without using additional
signaling between the first and second radio network controllers
105(1-N).
A stylized representation of a method is shown in FIG. 5 for the
first manager 124(1) to manage relocation of one or more scrambling
codes in the spread spectrum wireless communications system 100
shown in FIG. 1 at each of the first and second radio network
controllers 105(1-N) according to one illustrative embodiment of
the present invention. At block 500, an indication may be detected
for a serving radio network subsystem relocation that causes the
user equipment 110 to leave the first radio network controller
105(1). A check at a decision block 505 may ascertain whether or
not the indication causing relocation is available.
If so, at block 510, using the first buffer 122(1) may selectively
transit, through an intermediate transition, at least one
scrambling code of the one or more scrambling codes associated with
an uplink from the first radio network controller 105(1) to the
second radio network controller 105(N) for the user equipment 110.
In this way, using the FIFO register 400, the first manager 124(1)
may manage relocation of one or more scrambling codes in the spread
spectrum wireless communications system 100.
In some embodiments, a network vendor may deploy the first manager
124(1) to implement an assignment scheme of scrambling codes, which
have been relocated to from one RNC to other RNCs, where early
reuse may cause collisions. The first manager 124(1) may account
for a case where the UE 110 takes a scrambling code to another RNC
by the SRNS relocation. The first RNC 105(1) may maintain three
pools of scrambling codes, namely the first pool 405 of one or more
relocated scrambling codes (SCs), the second pool 410 of one or
more free scrambling codes and the third pool 415 for each of one
or more used scrambling codes. The handling of a SC transition
between the used and free SCs pool is set forth below.
The UE 110, upon a request may be assigned a SC from the second
pool 410 of one or more free scrambling codes and that particular
SC may be moved to the third pool 415 for each of one or more used
scrambling codes. If a call terminates, be it because of a regular
call termination or a failure, the SC goes back to the second pool
410 of one or more free scrambling codes. If the UE 110 has
relocated from a different RNC and has thus brought along a SC that
was not originally assigned to the current RNC then the RNC may
discard the SC upon the call termination.
When the UE 110 leaves the first RNC 105(1) due to SRNS relocation,
as described above, the associated SC may be moved to the first
pool 405 of one or more relocated scrambling codes, i.e., the first
manager 124(1) may cause transiting of the SCs from the first pool
405 of one or more relocated scrambling codes to either one of the
third pool 415 for each of one or more used scrambling codes or the
second pool 410 of one or more free scrambling codes.
However, if the UE 110 initiates a call such that no scrambling
codes may be available from the second pool 410 of one or more free
scrambling codes, a scrambling code from the first pool 405 of one
or more relocated scrambling codes may not be assigned at a cost of
a higher risk of collision. By using the first manager 124(1) to
transit SCs from the first pool 405 of one or more relocated
scrambling codes, a risk of collision, which depends upon a total
number of SCs available at an RNC, i.e., the total sizes of the
three pools, between UEs that may end up using the same scrambling
code may be obviated because there is no direct transition between
the pool 405 of one or more relocated scrambling codes and the
third pool 415 of free scrambling codes, as it is illustrated in
FIG. 4.
In this way, an uplink (UL) scrambling code may be assigned to a
particular UE. The scrambling code may be taken from the third pool
415 of free scrambling codes if this pool is not empty. If the
third pool 415 of free scrambling codes is empty, an UL SC from a
FIFO queue of the relocated UL SC pool may be taken. In both cases,
however, a particular SC may be moved to the third pool 415 of the
used scrambling codes. If a scrambling code from the SRNCs in the
third pool 415 of the used scrambling codes becomes free, a
call-teardown may be under way, causing a call to be dropped or
this scenario may happen due to other reasons. Thus, the SC may be
moved to the second pool 410 of the free scrambling codes and may
be immediately reused if desired.
If the UE 110 moves into a DRNC area and if the Iu connection is
relocated by a SRNS relocation procedure, the source RNC (old
serving RNC 105(1)) may store the UL SC in the first pool 405 of
the relocated UL SCs. This may avoid an early reuse, because the
target RNC 105(N) (new serving RNC) may use the same SC as long the
relocated UE 110 maintains the current call. The target RNC may
never use this UL scrambling code for its own UL scrambling code
assignments. When the UE 100 relocates from a different RNC and has
thus brings along a SC that was not originally assigned to the
current RNC, and then the first RNC 105(1) may discard the SC upon
the call termination for administration of the SCs.
Portions of the present invention and corresponding detailed
description are presented in terms of software, or algorithms and
symbolic representations of operations on data bits within a
computer memory. These descriptions and representations are the
ones by which those of ordinary skill in the art effectively convey
the substance of their work to others of ordinary skill in the art.
An algorithm, as the term is used here, and as it is used
generally, is conceived to be a self-consistent sequence of steps
leading to a desired result. The steps are those requiring physical
manipulations of physical quantities. Usually, though not
necessarily, these quantities take the form of optical, electrical,
or magnetic signals capable of being stored, transferred, combined,
compared, and otherwise manipulated. It has proven convenient at
times, principally for reasons of common usage, to refer to these
signals as bits, values, elements, symbols, characters, terms,
numbers, or the like.
It should be borne in mind, however, that all of these and similar
terms are to be associated with the appropriate physical quantities
and are merely convenient labels applied to these quantities.
Unless specifically stated otherwise, or as is apparent from the
discussion, terms such as "processing" or "computing" or
"calculating" or "determining" or "displaying" or the like, refer
to the action and processes of a computer system, or similar
electronic computing device, that manipulates and transforms data
represented as physical, electronic quantities within the computer
system's registers and memories into other data similarly
represented as physical quantities within the computer system
memories or registers or other such information storage,
transmission or display devices.
Note also that the software implemented aspects of the invention
are typically encoded on some form of program storage medium. The
program storage medium may be magnetic (e.g., a floppy disk or a
hard drive) or optical (e.g., a compact disk read only memory, or
"CD ROM"), and may be read only or random access. The invention is
not limited by these aspects of any given implementation.
The present invention will now be described with reference to the
attached figures. Various structures, systems and devices are
schematically depicted in the drawings for purposes of explanation
only and so as to not obscure the present invention with details
that are well known to those skilled in the art. Nevertheless, the
attached drawings are included to describe and explain illustrative
examples of the present invention. The words and phrases used
herein should be understood and interpreted to have a meaning
consistent with the understanding of those words and phrases by
those skilled in the relevant art. No special definition of a term
or phrase, i.e., a definition that is different from the ordinary
and customary meaning as understood by those skilled in the art, is
intended to be implied by consistent usage of the term or phrase
herein. To the extent that a term or phrase is intended to have a
special meaning, i.e., a meaning other than that understood by
skilled artisans, such a special definition will be expressly set
forth in the specification in a definitional manner that directly
and unequivocally provides the special definition for the term or
phrase.
While the invention has been illustrated herein as being useful in
a telecommunications network environment, it also has application
in other connected environments. For example, two or more of the
devices described above may be coupled together via
device-to-device connections, such as by hard cabling, radio
frequency signals (e.g., 802.11(a), 802.11(b), 802.11(g),
Bluetooth, or the like), infrared coupling, telephone lines and
modems, or the like. The present invention may have application in
any environment where two or more users are interconnected and
capable of communicating with one another.
Those skilled in the art will appreciate that the various system
layers, routines, or modules illustrated in the various embodiments
herein may be executable control units. The control units may
include a microprocessor, a microcontroller, a digital signal
processor, a processor card (including one or more microprocessors
or controllers), or other control or computing devices as well as
executable instructions contained within one or more storage
devices. The storage devices may include one or more
machine-readable storage media for storing data and instructions.
The storage media may include different forms of memory including
semiconductor memory devices such as dynamic or static random
access memories (DRAMs or SRAMs), erasable and programmable
read-only memories (EPROMs), electrically erasable and programmable
read-only memories (EEPROMs) and flash memories; magnetic disks
such as fixed, floppy, removable disks; other magnetic media
including tape; and optical media such as compact disks (CDs) or
digital video disks (DVDs). Instructions that make up the various
software layers, routines, or modules in the various systems may be
stored in respective storage devices. The instructions, when
executed by a respective control unit, causes the corresponding
system to perform programmed acts.
The particular embodiments disclosed above are illustrative only,
as the invention may be modified and practiced in different but
equivalent manners apparent to those skilled in the art having the
benefit of the teachings herein. Furthermore, no limitations are
intended to the details of construction or design herein shown,
other than as described in the claims below. It is therefore
evident that the particular embodiments disclosed above may be
altered or modified and all such variations are considered within
the scope and spirit of the invention. Accordingly, the protection
sought herein is as set forth in the claims below.
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